Update IVF_PQ array names (#511)

Author: jparismorgan

src/include/index/ivf_pq_group.h

@@ -45,9 +45,10 @@
 [[maybe_unused]] static StorageFormat ivf_pq_storage_formats = {
     {"0.3",
      {
-         // @todo Should these be kept consistent with ivf_flat?
-         {"cluster_centroids_array_name", "pq_cluster_centroids"},
-         {"flat_ivf_centroids_array_name", "uncompressed_centroids"},
+         // The centroids for each subspace.
+         {"cluster_centroids_array_name", "pq_subspace_centroids"},
+         // The centroids for each partition (of the original vectors).
+         {"flat_ivf_centroids_array_name", "partition_centroids"},
 
          // The partitioned, PQ-encoded vectors.
          {"pq_ivf_indices_array_name", "partitioned_pq_vector_indexes"},